In general, the present invention relates to a tensioning device used to adjust the counterbalance tension in a door system. More particularly, the present invention relates to a tensioning assembly that adjusts tension on a torsional counterbalance spring employed to offset the weight of a sectional door movable between an open position and a closed position.
A familiar door system is a sectional door system, which includes a plurality of panels that pivot sequentially as the door travels between a generally vertical closed position and a generally horizontal open position. It will be appreciated that, due to the weight of these doors, an ordinary user may not be able to lift the door without assistance. Thus, to provide a counterbalancing force for the weight of the door, a counterbalancing system is attached to the door, as by a cable. Typically, the counterbalancing system includes a drive shaft or tube having one or more cable drums about which the cable is coiled or uncoiled depending on the direction of door travel. A counterbalance spring associated with the drive tube rotationally biases the drive tube to provide the counterbalancing force to the door. During installation or assembly of the door system, the spring is appropriately tensioned to provide the necessary counterbalancing force. Optimally, the counterbalance spring would have sufficient tension such that the door would fully close while only a small amount of force would be necessary to raise the door from the closed position. If the proper tension is not initially attained or the tension falls out of the proper range over time, the installer or user may make appropriate adjustment by way of a tensioning assembly.
In many instances, the door tensioning assembly includes a winding cone attached to the counterbalance spring at one end and displaying one or more receiving sockets for the insertion of a winding bar. To tension the counterbalance spring, a bar is inserted into the winding cone to give the installer the necessary leverage to torque the spring as necessary to apply or release tension within the spring. It will be appreciated, however, that the use of such a tensioning assembly carries inherent danger to the installer. To remove some of these safety concerns, wormgear drives are used in some cases to adjust the tension on the counterbalance spring. The wormgear allows the installer to adjust tension by a hand drill or a ratcheting wrench. In one design available in the industry, a door system having a torsion bar and spring assembly is used to transmit a counterbalancing force to a door with a wormgear tensioning assembly employed to adjust and maintain tension on the spring. The spring is fastened by hooks at both ends to prevent axial and longitudinal movement thereof. The wormgear rotates on a casting that forms the mount for the worm and is fastened to the torsion bar. In this design, separate fasteners are required at each point of torque transmission including the worm housing, the worm gear, the drums, cables, and cable pins. Also, the wormgear must have a relatively large diameter to handle the short torque movement of the large springs and drums. The size of the worm gear tensioning assembly of this design makes it unsuitable for lower headroom structures.
In another worm tensioning assembly, available in the industry, a wormgear device is provided for use with conventional garage door springs. This design requires the counterbalance spring be mounted over the drive tube. The wormgear is detachable, and all of the tensioning components are secured with fasteners. A counter shaft is used to reverse the rotation of the worm allowing fine adjustment of the spring tension. As in the previously described design, the spring must be secured from axial and longitudinal movement. An allowance, however, is provided for alteration of the length of the spring, as a result of winding.
Still other tensioning assemblies employ a ratcheting system to adjust tension on the counterbalance spring. Tension is applied in much the same manner as the winding cone tension assembly, but, to reduce the risk of injury to the installer, tension is maintained by the pawl""s interaction with the gear teeth. One design, available in the industry, employs a collar, which can be slipped over the shaft around which the counterbalance spring is wound. The collar is fitted with a pair of ratcheting mechanisms and a device to hold these mechanisms in place. The collar is fastened to one end of the spring and turned to adjust the tension thereon. As the collar is rotated, the ratcheting mechanisms engage a boss on the collar to maintain the tension being applied to the spring.
Another design in the industry combines worm and ratchet systems in its tensioning assembly. This design includes a cone having a ring-shaped worm gear integrally formed thereon and attached to a counterbalance spring by way of a threaded connection. A worm drive is provided to rotate the ring-shaped spur gear. Rotation of the gear effects rotation of the cone, thereby adjusting tension on the counterbalance spring. A spring-loaded clip interacts with the gears to maintain the proper tension on the counterbalance spring.
In still another design, a ratcheting mechanism having a split housing is used to tension a counterbalance spring. Grooves are provided on either side of the split housing for receiving left and right hand ratcheting tools, which are simultaneously engaged and then used in sequence to create tension within the counterbalance spring. As in other designs, the ratcheting assembly prevents errant release of the spring""s tension.
While worm and ratchet tensioning devices of the type discussed above and other variations remove some of the danger associated with the winding cone tensioning assembly, they are more complex and require more parts making them more costly to produce. Additionally, due to their complexity and the need to create sufficient mechanical advantage to tension the spring, these systems are often large relative to the drive tube, track and other door assemblies requiring additional space for their installation and making them unsuitable for a number of applications.
It is, therefore, an object of the present invention to provide a less complex tensioning assembly for an upwardly acting sectional door system having fewer parts and therefore reducing cost. Another object of the present invention is to provide a tensioning assembly that includes a tension plate, which selectively interacts with a counterbalance assembly to apply tension to the counterbalance spring, and has locking members adapted to maintain the tension on the counterbalance spring. Yet another object of the invention is to provide such a tensioning assembly that may be selectively engaged with the counterbalance assembly incrementally to adjust the tension thereon by rotating the tensioning assembly.
It is another object of the present invention to provide a more compact tensioning assembly for a sectional door. Yet another object of the present invention is to provide a tensioning assembly that is received within conventional track members associated with a sectional door and requires minimal side clearance for adjustment. Still another object of the present invention is to provide a tensioning assembly that has a radial dimension similar to that of conventional cable drums in a sectional door system. A further object of the present invention is to provide a tensioning assembly having a smaller radial dimension than the cable drums in a sectional door system. A still further object of the present invention is to provide such a tensioning assembly which can be employed with either torsional springs or extension springs and which does not have gears having a tendency to fail and require replacement when a spring fails.
In view of at least one of the foregoing objects, the present invention generally provides a tension assembly for a door system, which includes an upwardly acting door supported by a frame and connected to a counterbalance system having a counterbalance spring, the tensioning assembly including a tension plate coupled to the counterbalance spring and rotatable relative to the counterbalance spring, the tension plate being selectively moveable between a disengaged position where the tension plate is freely rotatable and an engaged position where the tension plate is rotationally fixed to the frame; a spring adapted to urge the tension plate toward the engaged position, whereby when in the disengaged position the tension plate is rotated relative to the counterbalance spring to adjust a tension therein and the tension plate is returned to the engaged position to maintain the tension.
The present invention further provides a tensioning assembly including an upwardly acting door supported by a frame and connected to a counterbalance system having a counterbalance spring, the tensioning assembly including a locking member attached to the counterbalance spring moveable to an engaged position to maintain a selected tension on the counterbalance spring, and a release assembly operative to selectively disengage the locking member allowing adjustment of tension within the spring.